Simplex 4098 Applications Manual page 13

Where to Place Detectors and Sensors,
Proper Locations
When an air supply and/or an air return duct opening is present in a room or space, the
for Detectors
detector/sensor(s) should be placed in the path of the air flow toward the return air duct opening
and Sensors
(see below).
FigureTag FD4-709-02
Smoke tests are helpful in determining proper placement. Special attention should be given
to smoke travel directions and velocity, since either can affect detector/sensor performance.
Placement of a detector/sensor near air conditioning or incoming air vents can also cause
excessive accumulation of dust and dirt on the detector/sensor. This dirt can cause the
detector/sensor to malfunction and cause nuisance alarms. Detectors/sensors should not be located
closer than 3 feet (0.9 m) from an air supply diffuser.
Spot type detectors/sensors in properly engineered systems, may also be placed in return air ducts, or
in approved duct detector housings designed for this application. Although duct detectors are not a
substitute for open area detectors, they can provide an effective method of initiating building control
functions to prevent smoke from being transported from the fire area to other parts of a building.
Continued
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Figure 1-2. Detector Placement - Air Supply and/or Return Ducts
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